<html>
	<head></head>
	<body>
		<button id="btn1">show1</button>
		<button id="btn2">show2</button>
		<script>
			(function(){
				var a = 2;
				function show1()
				{
					alert('1, a is ' + a);
				}
				var o = document.getElementById('btn1');
				alert(o);///
				o.addEventListener('click', show1, false);
			})();
			(function(){
				var a = 4;
				function show1()
				{
					alert('2, a is ' + a);
				}
				var o = document.getElementById('btn2');
				alert(o);///
				o.addEventListener('click', show1, false);
			})();
		</script>
	</body>
</html>
